Simulation of Shock-Shear Interactions in Complex Domains

摘要

One Agent Defeat scenario of primary interest to the US Air Force involves the explosion of a warhead in ground-fixed target structures and storage facilities. Since, improper deployment can have potentially hazardous consequences, numerical studies can help understand the dynamics of this process. Simulation of this process requires a multi- physics code capable of treating both shocks and turbulence in complex geometries as well as single and multiphase chemistry. Smooth flow solvers can simulate turbulent flows, but these codes usually have significant difficulty in treating discontinuities such as shock waves without introducing unphysical oscillations into the flow. Shock capturing methods do a good job at treating shocks and contact discontinuities, but the dissipation in these methods can provide an incorrect treatment of the turbulent features in the flow. In this project, we have developed a hybrid code, which combines a high-order smooth-flow solver with a high-resolution shock-capturing method. The shock-capturing method is used only near discontinuities, while the smooth-flow solver is used to treat the remainder of the flow. The hybrid method is capable of producing solutions that are more accurate than could be obtained with either method by itself. The baseline code is LESLIE3D, a well-established DNS/LES solver developed for scalar mixing and combustion applications. Although LESLIE3D works very well for smooth flows, it cannot accurately handle strong shocks and contact discontinuities, which produce unphysical oscillations in the flow. A major accomplishment under this grant has been to incorporate a high-resolution shock- capturing method into the code. The scheme we use for shock capturing is the Piecewise-Parabolic Method (PPM) of Colella and Woodward. This method has been widely used, particularly for astrophysics calculations, where strong shocks appear on a regular basis.